1. Field of the Invention
The present invention relates to a printed circuit board, and more particularly to a printed circuit board of an electrical connector with high speed signal transmission
2. Description of Prior Arts
A conventional printed circuit board comprises plural conductive paths. The printed circuit board could be received in an electrical connector with high speed signal transmission. The conductive path comprises a soldering portion, an engaging portion, and a middle portion interconnected between the soldering portion and the engaging portion. The soldering portion is used for being soldered with a wire. The engaging portion is used for being mated with a mating terminal. When the engaging portion of the conductive path is mated with a mating portion of the mating terminal, a combined thickness of the mating portion and the engaging portion will be greater than a thickness of the middle portion. Likewise, when the soldering portion of the conductive path is soldered with a conductor of the wire, a combined thickness of the soldering portion and the conductor will be greater than a thickness of the middle portion. Therefore, when the electrical connector assembly is working, the characteristic impedance of the printed circuit board will have a discontinuity. That is, the characteristic impedance of the engaging portion is smaller than the characteristic impedance of the middle portion, and the characteristic impedance of the soldering portion is smaller than the characteristic impedance of the middle portion. This makes the transmission of the high speed signals unstable.
U.S. Pat. No. 7,088,200, issued to Bartley et al. on Aug. 8, 2006, discloses a method and structure to control common mode impedance in fan-out regions for printed circuit board applications. A differential pair transmission line includes a narrow signal trace portion in the fan-out region and a wider signal trace portion outside of the fan-out region. The narrow signal trace portion in the fan-out region has an increased thickness relative to the wider signal trace portion.
A printed circuit board with stable signal transmission is desired.